Resolve #3462514 "Link attributes with manager"

Closes #3462514

modules/graphql_compose_menus/src/Plugin/GraphQL/SchemaExtension/MenusSchemaExtension.php

@@ -10,6 +10,7 @@ use Drupal\graphql\GraphQL\ResolverBuilder;
 use Drupal\graphql\GraphQL\ResolverRegistryInterface;
 use Drupal\graphql_compose\Plugin\GraphQL\SchemaExtension\ResolverOnlySchemaExtensionPluginBase;
 use Drupal\menu_link_content\Plugin\Menu\MenuLinkContent;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 use function Symfony\Component\String\u;
 
@@ -25,6 +26,32 @@ use function Symfony\Component\String\u;
  */
 class MenusSchemaExtension extends ResolverOnlySchemaExtensionPluginBase {
 
+  /**
+   * Link attributes plugin manager.
+   *
+   * @var \Drupal\link_attributes\LinkAttributesManager|null
+   */
+  protected $linkAttributesManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    $instance = parent::create(
+      $container,
+      $configuration,
+      $plugin_id,
+      $plugin_definition
+    );
+
+    $instance->linkAttributesManager = $container->get(
+      'plugin.manager.link_attributes',
+      ContainerInterface::NULL_ON_INVALID_REFERENCE
+    );
+
+    return $instance;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -171,9 +198,18 @@ class MenusSchemaExtension extends ResolverOnlySchemaExtensionPluginBase {
     );
 
     $attributes = ['class'];
+
     if ($this->moduleHandler->moduleExists('menu_link_attributes')) {
-      $menu_link_attributes = $this->configFactory->get('menu_link_attributes.config')->get('attributes') ?: [];
-      $attributes = array_merge($attributes, array_keys($menu_link_attributes));
+      $attributes = array_merge(
+        $attributes,
+        array_keys($this->configFactory->get('menu_link_attributes.config')->get('attributes') ?: [])
+      );
+    }
+    elseif ($this->moduleHandler->moduleExists('link_attributes_menu_link_content')) {
+      $attributes = array_merge(
+        $attributes,
+        array_keys($this->linkAttributesManager->getDefinitions()),
+      );
     }
 
     foreach ($attributes as $attr) {